I will use this Thread as a collection of various Scripts and Hacks.
Suggestions are always welcome.

Grommunio-Admin

Completion

apt-get|zypper install bash-completion python3-argcomplete
eval "$(register-python-argcomplete grommunio-admin --complete)"
# OR
apt-get|zypper install bash-completion grommunio-admin-api-bash-completion

`grom_users` - Return List of all Users [ optional Filter on Domain ]

grom_doms() { grommunio-admin domain list |awk '{print $2}' ; }
grom_users() {
  local doms
  if [[ "$#" -ge 1 ]]; then
    doms=$(grep "^${1}" <<< "$(grom_doms)")
  else
    doms=$(grom_doms)
  fi
  for dom in $doms; do \
    grommunio-admin user query --format json-structured | \
    jq -r '.[]|select(.username|endswith("'"${dom}"'"))|.username'
  done
}

EXMDB - man

Folder-List (CSV) with HEX-ID's

grommunio-admin exmdb user@domain.de folder list --format csv -r |awk -F, '(NR>1) {printf "0x%x;%s\n", $1, $3}'

`exmdb_list_folders`

exmdb_list_folders() { 
  local U SHORT RE HEXIT
  case $1 in
    "$(grep "^$1" <<< $(grom_users))") 
      U="${1}"
      shift;;
    *)return 1;;
  esac
  for arg in "$@"
  do
    case "$arg" in
      -s) SHORT=1;;
      -r) RE="-r";;
      -h) HEXIT=1;;
      *);;
    esac
  done
  grommunio-admin exmdb "${U}" folder list --format csv $RE |sed '1d' |awk -F, '{print $1";"$3}' | while read LINE; do
  if [ ${HEXIT+x} ] ; then LINE=$(echo $LINE|awk -F";" '{printf "0x%x;%s\n", $1, $2}') ; fi
  if [ ${SHORT+x} ] ; then LINE=$(echo $LINE|cut -d";" -f1) ; fi
  echo "${LINE}"
done
}

`exmdb_get_permissions`

_exmdb_folders_long(){ exmdb_list_folders $1 -r -h ; }
_exmdb_folders_short(){ exmdb_list_folders $1 -r -h  -s ; }

#GetFolderPermissions
exmdb_get_permissions() {
  _grom_users="${_grom_users:=$(grom_users)}"
  local owner folders user folder
  if [[ "$_grom_users" =~ "$1" ]]; then
    owner="${1}"
    folders=${folders:="$(_exmdb_folders_long $owner)"}
    short=${short:="$(_exmdb_folders_short $owner)"}
    for name in $short; do
      echo $(grep "$name" <<< $folders)
      grommunio-admin exmdb "${owner}" folder permissions "${name}" ${user}
    done
  fi
}
complete -F _comp_grom_users exmdb_get_permissions

exmdb_set_stdFolders - Overwrite $_exmdb_std_folders

Example for MH that shouldn't have Full $Perms

# Default Folders
#  0x9;Oberste Ebene des Informationsspeichers
#  0xa;Gesendete Elemente
#  0xb;Gelöschte Elemente
#  0xc;Postausgang
#  0xd;Posteingang
#  0xe;Entwürfe
#  0xf;Kalender
#  0x10;Journal
#  0x11;Notizen
#  0x12;Aufgaben
_exmdb_std_folders="$(echo 0x{10..12} 0x{a..f})
exmdb_set_stdFolders() { 
  local owner user acl acls
  if [[ "$#" -ge 3 ]]; then
    owner="${1}"
    user="${2}"
    shift 2
    acls="${@}"
    grommunio-admin exmdb "${owner}" folder grant 0x9 "${user}" foldervisible
    for folder in ${_exmdb_std_folders}; do
      #hmmmm ... worked different $someday
      for acl in $acls; do
        grommunio-admin exmdb "${owner}" folder grant "${folder}" "${user}" "${acl}"
      done
    done
  fi
}
# completion
ACL="all create createsubfolder deleteany deleteowned editany editowned foldercontact folderowner foldervisible freebusydetailed freebusysimple readany sendas storeowner"
_comp_exmdb_set_stdFolders() {
  _grom_users="${_grom_users:=$(grom_users)}"
  local cur
  COMPREPLY=()
  cur="${COMP_WORDS[COMP_CWORD]}"
  case $COMP_CWORD in
    1)
      COMPREPLY=( $(compgen -W "${_grom_users}" -- ${cur}) )
      ;;
    2)
      COMPREPLY=( $(compgen -W "${_grom_users}" -- ${cur}) )
      ;;
    *)
      COMPREPLY=( $(compgen -W "\$ACL ${ACL}" -- ${cur}) )
      ;;
  esac
  return 0
}
complete -F _comp_exmdb_set_stdFolders exmdb_set_stdFolders

Cleaning

Empty "Deleted Items"

_grom_query_maildir(){
  grommunio-admin user query --filter username="${1}" maildir
}
_grom_query_trashbin_count() {
  local user mdir sel
  _grom_users="${_grom_users:=$(grom_users)}"
  if [[ "$#" -eq 0 ]]; then
    for user in $_grom_users; do
      printf "%s;%s\n" $user $(_grom_query_trashbin_count "${user}")
    done
  fi
  if [[ "$#" -eq 1 ]]; then
    if [[ "$_grom_users" =~ "$1" ]]; then
      user="$1"
      mdir="$(_grom_query_maildir ${user})/exmdb/exchange.sqlite3"
      sel="select count(message_id) from messages where parent_fid=0xb;"
      echo $(sqlite3 ${mdir} "${sel}")
    fi
  fi
}

_grom_query_trashbin_ids() {
  local user mdir sel
  if [[ "$#" -eq 1 ]]; then
    _grom_users="${_grom_users:=$(grom_users)}"
    if [[ "$_grom_users" =~ "$1" ]]; then
      mdir="$(_grom_query_maildir $1)/exmdb/exchange.sqlite3"
      sel="select message_id from messages where parent_fid=0xb;"
      echo $(sqlite3 ${mdir} "${sel}")
    fi
  fi
}

_grom_delete_trashbin_id() {
  local user msgid
  if [[ "$#" -eq 2 ]]; then
    _grom_users="${_grom_users:=$(grom_users)}"
    if [[ "$_grom_users" =~ "$1" ]]; then
      user="$1"
      msgid="$2"
      (
      echo -ne "${user}: ${msgid} "
      /usr/libexec/gromox/delmsg -u "${user}" -f 0xb "${msgid}" 
      ) | logger -t _grom_delete_trashbin_id 
    fi
  fi
}

_grom_empty_trashbin() {
  local user msgid
  _grom_users="${_grom_users:=$(grom_users)}"
  if [[ "$#" -eq 0 ]]; then
    for user in $_grom_users; do
      _grom_empty_trashbin "${user}"
    done
  fi
  if [[ "$#" -eq 1 ]]; then
    if [[ "$_grom_users" =~ "$1" ]]; then
      user="$1"
      logger -t grom_empty_trashbin "$user"
      for msgid in $(_grom_query_trashbin_ids ${user}); do
        _grom_delete_trashbin_id ${user} ${msgid}
      done
    fi
  fi
}

Cleanup orphaned content

_grom_query_maildir(){
  grommunio-admin user query --filter username="${1}" maildir
}
grom_cleanup() {
  local maildir
  MESSAGE="\n\n\tTo really cleanup use: "$(blue "grom_cleanup")" "$(red "clean")"\n"
  SWITCH="-n";
  if [[ "$1" = "clean" ]]; then SWITCH="";MESSAGE=""; fi
  for user in $(grom_users); do
    yellow "User: ${user}:"
    maildir="$(_grom_query_maildir $user)"
    /usr/libexec/gromox/cleaner "${SWITCH}" -d "${maildir}" |grep --color=always -e "^" -e "[^ ]*[0-9](M|G)B" 
  done
  echo -e "$MESSAGE"
}

VACUUM SQLITE-DB's

systemctl stop gromox-http.service
for db in /var/lib/gromox/user/*/*/exmdb/exchange.sqlite3; do sqlite3 "$db" 'VACUUM;'; done
systemctl start gromox-http.service

Simple Bash-Completion

# completion
_comp_grom_users() {
  _grom_users="${_grom_users:=$(grom_users)}"
  local cur
  COMPREPLY=()
  cur="${COMP_WORDS[COMP_CWORD]}"
  case $COMP_CWORD in
    1)
      COMPREPLY=( $(compgen -W "${_grom_users}" -- ${cur}) )
      compopt +o nospace
      ;;
  esac
  return 0
}
complete -F _comp_grom_users _grom_query_trashbin_count _grom_query_maildir _grom_query_trashbin_ids _grom_empty_trashbin

ShellCheck!

zypper in ShellCheck
#OR
apt-get install shellcheck

Grommunio-Admin

Completion

grom_users - Return List of all Users [ optional Filter on Domain ]

EXMDB - man

Folder-List (CSV) with HEX-ID's

exmdb_list_folders

exmdb_get_permissions

exmdb_set_stdFolders - Overwrite $_exmdb_std_folders

Cleaning

Empty "Deleted Items"

Cleanup orphaned content

VACUUM SQLITE-DB's

Simple Bash-Completion

ShellCheck!

`grom_users` - Return List of all Users [ optional Filter on Domain ]

`exmdb_list_folders`

`exmdb_get_permissions`